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Software Development
SD Best Practices 2004 / Show Daily /

Common Sense Scrum

Ken Schwaber touts his management-focused process's versatility.

"Scrum isn't an engineering process," Ken Schwaber announced in his Tuesday morning class, "Scrum and Agile 101," at SD Best Practices in Boston, Mass. "It's a project management process." Schwaber, president of Advanced Development Methods Inc., and Jeff Sutherland, CTO of PatientKeeper Inc., developed Scrum in the early '90s. Scrum, one of the largest implementations of agile practices, has its origins, along with XP, in the Smalltalk language and object-oriented development.

"What do I do?," Schwaber asked. "I help people build software in 30 days." Scrum is no silver bullet; it's not prescriptive, he warned, telling the nearly full room that Scrum depends on common sense. Rather than setting out a detailed plan, Schwaber continued, we set out a vision that we use to manage the project. It's kind of contrary to the traditional project, he said, where it's cheap to make changes at the beginning and costs more at the end.

Software development is an extremely complex business, Schwaber continued, but agile processes give you complete control of your projects by letting you see everything that's happening. "You have an opportunity to fix something when it goes wrong," he said.

The bad news? There's so much that can go wrong in a software project, you can sometimes be overwhelmed with information. "I tell people, don't bother with Scrum unless building software is the most important thing to you," said Schwaber.

XP and Scrum

While Scrum and XP share similar origins, the two agile practices have different focuses. "We're often asked how XP and Scrum relate," said Schwaber. "Jeff Sutherland and I used Scrum to manage our processes as we ran a company," he relates. "Kent Beck used XP to engineer software."

According to Schwaber, Scrum is management-focused, while XP is engineering-focused; it's used to build software. In fact, Scrum can be used to manage anything, he quipped, telling the audience that he'd recently used XP to modify the engineering practices in Scrum. "It's a wrapper for anything—waterfall and RUP. It's a way of addressing a complex problem."

Scrum also has longer iterations than XP, he continued, referring to Scrum's 30-day sprints. "How did you decide that 30 days was right?" an audience member asked. "Empirically," Schwaber answered, "over 12 years. It's the time a team need to turn requirements into an increment. At six weeks, the team starts to need internal documents to remember past decisions."

Scrum can be implemented in just two days (XP takes longer), he continued, listing further differences. Also, in Scrum, estimates improve with time, while XP adherents try to make their estimates as precise as possible. Finally, XP tends to be specification-driven.

Into the Future

According to Schwaber, there are 970 trained Scrum masters, the equivalent of PMI project managers. "Scrum is no longer a rare thing," he enthused. In fact, none of the agile processes are rare any longer. More than 50 organizations have produced successful projects using Scrum. However, Schwaber doesn't expect that all organizations will welcome agile practices with open arms. "Why did we keep the name Scrum?" he asked. "So you wouldn't use it." Don't tell your customer that you have a new process, he advised the audience, telling them to just use it and deliver working software.

—Tamara Carter

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